Exekn.m Exelon Generation Telephone 610.765.5661 Generati on 200 Exelon Way Fax 610.765.5545 KSA3-N www.exeloncorp.com Kennett Square, PA 19348 Project No.: 713 August 30, 2001 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Subject: "Introduction to the Pebble Bed Modular Reactor" Dear Sir/Madam, a general Transmitted here with is a copy of the subject document, which provides presents an description of the Pebble Bed Modular Reactor (PBMR). This document safety analysis, and overview of the PBMR; the concept, the basic principles of design, operation. It is not intended to be used (or maintained) as a design document. Sincerely, Manager, Licensing PBMR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-185 PBMR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-1 85 INTRODUCTION TO THE PEBBLE BED MODULAR REACTOR (PBMR) DOCUMENT No.: 009949-185 Revision: 1 Document Status: Approved 1 Page 1 0179 ©@ Copyright 20012001 by PBMR 22/08/200122108/2001 Revision 1 Page 1 of 79 PBMVR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-185 CHANGE HISTORY Configuration Control Project: PBMR Title: Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. Reference: 009949-185 Created By: A P George Creation Date: August 2001 Classification: Confidential Document History Revision History Revision Date Changes A August 2001 New document 1 August 2001 Document updated after review I Page 2of79 Q© Copyright 2001 byby PB3MRPBMR 22/08/200122108/2001 Revision I Page 2 of 79 PBMVR Introduction to the Pebble Bed Modular Reactor (PBMVR) Doc. No. 009949-185 PBMR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-1 85 Management Authorization Change Forecast Subject to negotiated changes. I Page 3 of 79 Q© Copyright 20012001 by PBMR 22108/2001 Revision I Page 3 of 79 PBMR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-185 CONTENTS LIST O F ABREVIATIONS .................................................................................................................................. 8 KEY NON-APPLICABLE LIGHT W ATER REACTOR TERMS .................................................................. 11 1. GENERAL DESCRIPTION AND TECHNOLOGY OVERVIEW ............................................. 12 1.1 Introduction .................................................................................................................................. 12 1.2 General Description ..................................................................................................................... 12 1.2.1 Technical design philosophy .................................................................................................. 12 1.2.2 Normal operation ......................................................................................................................... 13 1.3 Key Features ............................................................................................................................... 14 1.4 Technology .................................................................................................................................. 15 2. REACTOR UNIT .......................................................................................................................... 17 2.1 Introduction .................................................................................................................................. 17 2.2 Major Features and Internal Com ponents .............................................................................. 18 2.2.1 Reactor pressure vessel .......................................................................................................... 18 2.2.2 Core structures ............................................................................................................................ 19 2.3 Major Support Systems ......................................................................................................... 26 2.3.1 Reactor cavity cooling system ................................................................................................ 26 2.3.2 Reactor unit conditioning system ............................................................................................ 28 2.3.3 Helium inventory control system ............................................................................................ 28 2.3.4 Fuel handling and storage system .......................................................................................... 31 2.4 Reactivity Control and Shutdown System ............................................................................. 33 2.4.1 System description and drawings ................................................................................................ 33 . 2.4.2 Testing and inspection plan ..................................................................................................... 36 3. FUEL ............................................................................................................................................ 39 3.1 Summ ary ..................................................................................................................................... 39 3.2 Fuel Elem ents (Spheres) ....................................................................................................... 39 3.2.1 Fuel kernel ................................................................................................................................... 39 3.2.2 Fuel elem ent matrix ..................................................................................................................... 40 3.2.3 Fuel-free zone ................................................................................................................... 40 3.3 Fuel Operation ............................................................................................................................. 41 3.4 Fuel Perform ance ........................................................................................................................ 42 4. THERMO DYNAM ICS .................................................................................................................. 43 4.1 Brayton Cycle .............................................................................................................................. 43 5. POW ER CONVERSION UNIT .............................................................................................. 47 5.1 Introduction .................................................................................................................................. 47 5.2 Major Features and Components ............................................................................................ 47 5.2.1 Turbo-units ................................................................................................................................... 47 5.2.2 Power turbine generator .......................................................................................................... 48 5.2.3 Recuperator ................................................................................................................................. 48 © Copyright 2001 by PBMR 22/08/2001 Revision 1 Page 4 of 79 PBMR Introduction to the Pebble Bed Modular Reactor (PBMR) Doc. No. 009949-185 5.2.4 Cycle heat exchangers (pre-cooler and intercooler) ............................................................. 49 6. MAJOR DESIGN FEATURES AND AUXILIARY SYSTEMS ................................................ 50 6.1 Pressure Boundary System ................................................................................................... 50 6.1.1 Vessel system .............................................................................................................................. 50 6.1.2 Vessel support system ................................................................................................................. 52 6.1.3 Pressure relief system ................................................................................................................. 52 6.2 Helium Inventory Control System ............................................................................................ 53 6.3 Auxiliary Systems ........................................................................................................................ 53 6.3.1 Active cooling system .................................................................................................................. 53 6.3.2 Reactor cavity cooling system ................................................................................................ 54 6.3.3 Used fuel cooling system ........................................................................................................ 54 6.3.4 Heating ventilating and air conditioning system .................................................................... 55 6.3.5 Airlocks ........................................................................................................................................ 56 6.3.6 Primary loop initial clean-up system ....................................................................................... 57 6.3.7 Com pressed air system .......................................................................................................... 57 6.3.8 Pressure relief system ................................................................................................................